The compounds of formula I are important intermediates for the preparation of, e.g., phosphoric acid esters of substituted hydroxypyrimidines as disclosed and claimed in U.S. Pat. No 2,754,243 and in particular 0,0-diethyl-0-(2-isopropyl-4-methyl-6-pyrimidyl)-thiophosphate (DIAZINON) which has great commercial value. It is a well-established insecticide and acaricide and is useful in pest control.
These substituted hydroxypyrimidines have been produced in commercial practice in a laborious multi-step manner as follows: ##STR2##
Recently the above conventional manufacturing process has been improved and optimized by a continuous ring-closure/neutralization process as claimed in U.S. Pat. No. 4,014,879, issued Mar. 29, 1977.
Alternate processes for the preparation of these hydroxypyrimidines have been published in the Japanese Patent literature. Japanese Pat. No. 557,103 teaches that these hydroxypyrimidines can be prepared by various heat treatments from .beta.-acylaminocrotonamides prepared from .beta.-aminocrotonamides (derived from diketene and ammonia) and acid halides or anhydrides. According to published Japanese Patent Application SHo-48-39-942 these hydroxypyrimidines can be prepared by reacting .beta.-aminocrotonamide and an organic acid ester in the presence of certain alkaline reactants such as alkali metals or their alcoholates.
Recently there have been patented alternate ways of preparing the compounds of Formula I including U.S. Pat. No. 3,618,771, which issued Apr. 19, 1977 and U.S. Pat. No. 4,052,396 and U.S. Pat. No. 4,052,397, which issued on Oct. 4, 1977.
U.S. Pat. No. 4,018,771 teaches the synthesis of these compounds by reacting diketene with lower alkanoic acid amides in the presence of catalysts and then treating the resulting N-acetoacetyl alkanoic acid amides with ammonia in the presence of acidic catalysts.
U.S. Pat. No. 4,052,396 discloses the reaction of diketene with alkanoic acid nitriles in the presence of acidic catalysts followed by the treatment of the reaction product with ammonia.
U.S. Pat. No. 4,052,397 discusses the preparation of the hydroxypyrimidines of Formula I by sequentially treating, in organic solvent, diketene with ammonia and then treating the resulting .beta.-aminocrotonamide, after water removal, with an alkanoic acid ester and an alkali metal alkoxide.
However, all of these prior art procedures leave something to be desired from the standpoint of efficient economical large-scale commercial manufacturing. It is an object of this invention to provide a better synthetic route to these materials.